Disclosed herein is a method for making a new crystalline form of cyclosporin A.
Cyclosporin A
Cyclosporin A (CsA) is a cyclic peptide having the following chemical structure:

Its chemical name is cyclo[(E)-(2S,3R,4R)-3-hydroxy-4-methyl-2-(methylamino)-6-octenoyl]-L-2-aminobutyryl-N-methylglycyl-N-methyl-Lleucyl-L-valyl-N-methyl-L-leucyl-L-alanyl-D-alanyl-N-methyl-L-leucyl-N-methyl-L-leucyl-N-methyl-L-valyl]. It is also known by the names cyclosporin, cyclosporine A, ciclosporin, and ciclosporin A. It is the active ingredient in RESTASIS® (Allergan, Inc., Irvine, Calif.), an emulsion comprising 0.05% (w/v) cyclosporin. RESTASIS® is approved in the United States to increase tear production in patients whose tear production is presumed to be suppressed due to ocular inflammation associated with keratoconjunctivitis sicca.
Cyclosporin A is known to exist in an amorphous form, liquid crystal form, tetragonal crystalline form (Form 1), and an orthorhombic form (Form 3). The inventors describe here a method of making a new crystalline form, cyclosporin A Form 2.